We propose to continue studies of the role of lectins in development of embryonic chick tissues and slime mold cells. In the past year we have extended to three the number of developmentally regulated chicken lectins that we have purified. Two arelactose-binding lectins and are called chicken-lactose-lectin-I and chicken-lactose-lectin-II; and the third which binds geparin and N-acetyl-galactosamine is called chicken-heparin-lectin. We propose to determine the quantity of these lectins in different tissues and at different stages of chick development using a radioimmunoassay; and to localize the lectins with chick tissues by immunohistochemistry. Our work with slime molds is concentrated on purpurin, the lectin from Dictyosteium purpurem, which we have recently found to exist in seven distinct forms which we have now separated. We propose to determine the developmental regulation and distribution of these forms. Efforts to identify and localize endogenous receptors for slime mold lectins continue.